1. Field of the Invention
The present invention relates to a local area network (LAN) system with a multi-computer system coupled thereto, and, more particularly, to a communication method for ensuring effective communication of transfer frames by assigning the same address to a multi-computer system and a LAN system for realizing the same.
2. Description of the Related Art
Conventionally, it is unlikely that a multicomputer system is coupled to a LAN. From typical ways of providing connection to a LAN, there are two methods available for coupling a multi-computer system to the LAN. The first one is to allow individual computers to have their own communication controllers through which they are coupled to a LAN cable. To specify the individual communication controllers on the LAN, the controllers should have different or unique addresses in accordance with the rules of the LAN. Accordingly, an external computer that needs communication with a multi-computer system should have some means to detect which computer of the system is presently active or a master and should send data to the communication controller coupled to that computer. However, this detection means has a complicated structure and requires such means as PIO (process input/output) and system control programs, so that it is not suitable for a general use, nor is it cost-effective.
The second method is to couple a single communication controller to a multi-computer system via a multi-computer bus such that the individual computers constituting the system are coupled to a LAN cable through the controller. Although overcoming the problem of the first system, the second system needs means for informing the communication controller of which computer is active and means for effecting data transfer between the active computer and controller itself over the multi-computer bus. Generally, this type of bus needs more complicated control and has a lower speed as compared with internal buses of the computers. This obstructs effective utilization of the high-speed communication of the LAN (typically, 2 to 100 Mbps) and increases the manufacturing cost.